The present invention relates to ferrules and associated optical fiber connectors, and, more particularly, to a ferrule that may be universally used with a plurality of connectors.
The use of optical fiber for transmitting information, such as data or voice communications, is increasing. Optical fiber offers advantages over traditional copper wire due to the improved transmission speed and larger information capacity for the same sized cable, among other reasons. Due to the proliferation of uses for optical fiber, there has been a corresponding proliferation of connectors used to terminate and couple one or more optical fibers to other optical fibers or to other terminals. These connectors include connectors for a single optical fiber, for two optical fibers, and for more than two optical fibers (usually in multiples of two). Connectors for two or more optical fibers are desirable since they allow simultaneous transmission and reception of information.
Such connectors include configurations that generally define the positioning of the one or more optical fibers within the connector, as well as the structure for securing the connector to other connectors or terminals. For example, a number of different types of connectors for a single optical fiber include SC, FC, ST, and D4 connectors. Similarly, a number of different types of connectors for two optical fibers include the MT and MT-RJ connectors, as well as the SC-DC(trademark) and UNICAM(copyright) connectors produced by the assignee of the present invention.
Even though numerous types of connectors exist, some of the connector components between the types are similar. For example, each type of connector generally includes a ferrule for terminating at least one optical fiber and a housing for holding the ferrule and coupling with other connectors or terminals. A ferrule typically has a shaft-like body and a base. Generally, a ferrule with a circular base has a corresponding cylindrical body, while a ferrule with a square or rectangular base has a square or rectangular shaft-like body. The base engages an internal chamber within the housing to position the ferrule. Meanwhile, the shaft-like body positions the one or more optical fibers relative to corresponding fibers in a mating connector or terminal.
Although similar, the components for one type of connector generally cannot be used in another type of connector. In particular, ferrules are generally not interchangeable among connector types. Typically, there are differences in the internal structures of the housings of the connectors, thus requiring different shaft-like bodies and/or bases for the ferrule. As mentioned above, the internal housing structure may require a ferrule having a round, square, or rectangular base and/or shaft. As such, ferrules with square bases typically do not fit properly within connector housings having round internal structures, and vice versa. This lack of interchangeability of ferrules between connector types requires extra cost in manufacturing, where extra equipment is required to produce the various ferrules, and extra time is spent to manage, schedule, and stock the various ferrules. Also, the multitude of required ferrules adds time and cost to installation and replacement of connectors, as the proper ferrule must be determined and kept in stock.
Further, differences in the external surface of the body of the ferrule lead to problems in aligning mating ferrules. The alignment of optical fibers within mating ferrules is often dependent on the external surface of each ferrule, as coupling sleeves and/or guide pins often engage these surfaces to align the ferrules. With single fiber ferrules, the fiber is typically aligned along the central axis of the ferrule such that rotation of the ferrule does not cause misalignment between mating fibers. In contrast, multi-fiber ferrules, which typically include 2, 4, 8, 12, or 24 fibers, cannot allow rotation between mating ferrules as the fibers would become misaligned. The engagement of the ferrule base with the internal housing of the connector provides an initial alignment. But, as mentioned above, more precise alignment is provided by coupling sleeves and/or guide pins that engage the external surface of the ferrule. The ferrules or the coupling sleeves for ferrules have alignment devices, such as guide pins, ribs, or a portion of a guide pin, to align mating ferrules and prevent rotation between the ferrules. It is often difficult to maintain the required dimensional tolerances on the external body surface, especially for molded thermoplastic ferrules, to guarantee proper alignment of mating ferrules. Further, any misalignment during the initial engagement of the ferrule with an alignment sleeve or guide pin can lead to chipping or scraping of material from the surface of the ferrule, thereby causing further alignment problems.
Thus, a ferrule that is adapted for universally fitting within a multitude of types of connectors is desired. Further, a ferrule having improved alignment with a mating ferrule is also desired. Finally, a ferrule having a body that more easily aligns with a guide pin or sleeve for connection with another ferrule is desired. Therefore, a universal ferrule with enhanced alignment features is desired.
The present invention advantageously includes a universal ferrule for positioning at least one optical fiber within a plurality of types of optical fiber connector housings. Preferably, the plurality of types of housings include single fiber and multiple fiber housings. The universal ferrule includes a longitudinal body having first and second ends, where the body further includes at least one longitudinal bore for receiving the optical fiber extending between the ends. The universal ferrule includes an end face at the first end, where the end face interfaces with a corresponding end face of a mating ferrule. Further, the universal ferrule includes a base adapted to interchangeably engage a plurality of connector housings to, inter alia, position the ferrule relative to the housing. The base preferably radially extends outwardly from the body and is sized and shaped to rotationally, radially, and longitudinally position the ferrule relative to the housing. In one embodiment, the base includes at least two substantially flat side portions that are adapted to engage the corresponding housing. In another embodiment, the base is substantially rectangular and has edges that are adapted to fit within various shaped housings, including circular, arcuate, square, and rectangular housings.
Further, the body of the universal ferrule is preferably cylindrical. The cylindrical body may include at least one longitudinal groove adapted for positioning the ferrule relative to a mating ferrule. The groove may additionally include a first groove portion adjacent to the first end and a second groove portion adjacent to the second end. In this embodiment, only the first groove portion is adapted for positioning the universal ferrule relative to a mating ferrule. As such, the first groove portion is typically smaller in size than the second groove portion. Preferably, the first and second groove portions have a first and second radius, respectively, where the first radius is less than the second radius. Other configurations for the groove, such as square, rectangular, v-shaped, or arcuate-shaped channels, may also be utilized.
Further, in one embodiment, the present invention comprises a system for terminating an optical fiber cable having at least one optical fiber. The system includes a connector type, selected from a plurality of optical fiber connectors, that includes a housing having an internal chamber. The system also includes a universal ferrule adapted for insertion within the internal chamber to position the ferrule relative to the housing. The ferrule includes a body and base, similar to those described above, where the base is adapted to engage the internal chamber to rotationally, radially, and longitudinally position the ferrule relative to the housing. In this embodiment, the plurality of optical fiber connectors include single fiber and multiple fiber connectors, such as the SC, SC-DC(trademark), MT-RJ UNICAM(copyright), and MT-RJ connectors. The system may further include a sleeve for aligning mating ferrules.